General procedure for the synthesis of 1,3-dihydro-1-(1-methylethynyl)-2H-benzimidazol-2-one from ethyl acetoacetate and o-phenylenediamine: 50 grams of o-phenylenediamine, 90 grams of ethyl acetoacetate, and 5 grams of sodium hydroxide were dissolved in 300 ml of o-xylene. The reaction was refluxed at 130°C for about 7 hours, during which time the water generated was removed by means of a water separator. Upon completion of the reaction, the reaction mixture was cooled to 80 °C and washed twice with 100 ml of water to remove water-soluble impurities. Subsequently, the mixture was cooled to 0 °C to allow the target product to precipitate as a white solid. The solid product was collected by filtration and dried to give 65 g of 1,3-dihydro-1-(1-methylethynyl)-2H-benzimidazol-2-one (DOM-2) in 94% yield.
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